Voice coil motor

ABSTRACT

A VCM is disclosed, the motor including a stator including a first driving unit, a rotor arranged inside the stator, including a second driving unit responding to the first driving unit and mounted therein with a lens, a base fixing the stator, and an elastic member coupled to the rotor to float the rotor from the base in a case a driving signal for driving the first and second driving units is not applied to the first and second driving units.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. §119 of KoreanPatent Application Nos. 10-2011-0119348, filed Nov. 16, 2011,10-2011-0145805, filed Dec. 29, 2011, and 10-2011-0145808, filed Dec.29, 2011, which are hereby incorporated by reference in their entirety.

BACKGROUND

1. Field of the Invention

The present disclosure relates to a VCM (Voice Coil Motor), and moreparticularly to a voice coil motor enabling to bi-directionally drive arotor using a small current by floating the rotor from a base.

2. Description of Related Art

Recently, a mobile phone embedded with a super small digital camera hasbeen developed. A conventional super small digital camera used on amobile phone has suffered from a disadvantage of disablement to adjust agap between a lens and an image sensor changing an outside light to adigital image or a digital video (moving image). However, recently, alens driving device such as a voice coil motor capable of adjusting agap between an image sensor and a lens has been developed to obtain adigital image or a digital video more advanced than that of aconventional super small digital camera.

Generally, a VCM (Voice Coil Motor) is mounted therein with a lens,where a bobbin arranged on a base is vertically moved from the base toadjust a gap between an image sensor arranged at a rear surface of thebase and a lens of the camera. The bobbin of the VCM is coupled with aleaf spring to be always brought into contact with the base by elasticforce of the leaf spring when the VCM is not operated. That is, theconventional VCM is driven only to one direction relative to the base.

Because the conventional VCM is driven only to one direction, the VCMdisadvantageously needs a driving force greater than a self-weight ofthe bobbin and the elastic force of the leaf spring to drive the VCM,causing a greater increase in power consumption of the VCM. Theconventional VCM further suffers from a disadvantage in that, because itneeds a driving force greater than a self-weight of the bobbin and theelastic force of the leaf spring, size of coil wound on the bobbin orthe leaf spring increases to increase an entire size of the VCM.

BRIEF SUMMARY

The present invention is directed to provide a VCM configured to improvequality of an image by floating the rotor from a base to allow the rotorto bi-directionally drive with a small amount of current, and byrealizing a focusing using, by a rotor, a stabilized section, instead ofusing a rotor un-stabilized section where a rotor is tilted or shakenduring driving. The present invention is also directed to provide a VCMconfigured to inhibit or restrict a tilting of a rotor generated inresponse to posture of the rotor, and to further reduce powerconsumption when an infinite focusing area is used.

Technical problems to be solved by the present disclosure are notrestricted to the above-mentioned descriptions, and any other technicalproblems not mentioned so far will be clearly appreciated from thefollowing description by skilled in the art.

An object of the invention is to solve at least one or more of the aboveproblems and/or disadvantages in whole or in part and to provide atleast the advantages described hereinafter. In order to achieve at leastthe above objects, in whole or in part, and in accordance with thepurposes of the invention, as embodied and broadly described, and in onegeneral aspect of the present invention, there is provided a VCM, theVCM comprising: a stator including a first driving unit; a rotorarranged inside the stator, including a second driving unit respondingto the first driving unit and mounted therein with a lens; a base fixingthe stator; and an elastic member coupled to the rotor to float therotor from the base in a case a driving signal for driving first andsecond driving units is not applied to the first and second drivingunits.

The VCM according to the present disclosure has an advantageous effectin that a rotor is floated from an upper surface of a base when adriving signal is not applied, and a length of a stroke length or a gapbetween the floated rotor and the upper surface of the base isdifferently formed from a stroke length or a gap between the floatedrotor and the cover to realize a low current consumption characteristicor a low power consumption characteristic.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, the width, length, thickness, etc. of components may beexaggerated or reduced for the sake of convenience and clarity.Furthermore, throughout the descriptions, the same reference numeralswill be assigned to the same elements in the explanations of thefigures, and explanations that duplicate one another will be omitted.Now, a voice coil motor according to the present disclosure will bedescribed in detail with reference to the accompanying drawings.

The teachings of the present disclosure can be readily understood byconsidering the following detailed description in conjunction with theaccompanying drawings, in which:

FIG. 1 is a schematic cross-sectional view illustrating a VCM accordingto a first exemplary embodiment of the present disclosure;

FIG. 2 is an exploded perspective view of an entire configuration of theVCM of FIG. 1;

FIG. 3 is an assembled cross-sectional view of FIG. 2;

FIG. 4 is a cross-sectional view illustrating a VCM based on acomparative example in contrast to the VCM according to the firstexemplary embodiment of the present disclosure;

FIG. 5 is a cross-sectional view illustrating the VCM in contrast to thecomparative example of FIG. 4 according to the first exemplaryembodiment of the present disclosure;

FIG. 6 is a cross-sectional view illustrating a VCM based on a secondcomparative example in contrast to the VCM according to the firstexemplary embodiment of the present disclosure;

FIG. 7 is a cross-sectional view illustrating a VCM based on the secondcomparative example of FIG. 6 in contrast to the VCM according to thefirst exemplary embodiment of the present disclosure;

FIG. 8 is a schematic cross-sectional view illustrating a VCM accordingto a second exemplary embodiment of the present disclosure;

FIG. 9 is a graph illustrating a current-distance characteristic and acurrent-tilt amount characteristic of a rotor of FIG. 8;

FIG. 10 is a schematic cross-sectional view illustrating a VCM accordingto a third exemplary embodiment of the present disclosure;

FIG. 11 is a graph illustrating a current-distance characteristic of aVCM of FIG. 8;

FIG. 12 is a cross-sectional view illustrating a state of a reversed VCMof FIG. 10; and

FIG. 13 is a schematic cross-sectional view illustrating a VCM accordingto another exemplary embodiment of the present disclosure.

DETAILED DESCRIPTION

Advantages and features of the present disclosure may be understood morereadily by reference to the following detailed description of exemplaryembodiments and the accompanying drawings.

Detailed descriptions of well-known functions, configurations orconstructions are omitted for brevity and clarity so as not to obscurethe description of the present disclosure with unnecessary detail. Thus,the present disclosure is not limited to the exemplary embodiments whichwill be described below, but may be implemented in other forms.

The meaning of specific terms or words used in the specification andclaims should not be limited to the literal or commonly employed sense,but should be construed or may be different in accordance with theintention of a user or an operator and customary usages. Therefore, thedefinition of the specific terms or words should be based on thecontents across the specification.

Now, exemplary embodiments of a VCM (Voice Coil Motor) according to thepresent disclosure will be explained in detail together with thefigures.

First Exemplary Embodiment

FIG. 1 is a schematic cross-sectional view illustrating a VCM accordingto a first exemplary embodiment of the present disclosure, FIG. 2 is anexploded perspective view of an entire configuration of the VCM of FIG.1, and FIG. 3 is an assembled cross-sectional view of FIG. 2.

Referring to FIGS. 1, 2 and 3, a voice coil motor (hereinafter referredto as VCM, 600) may include a stator (100), a rotor (200), a base (300)and an elastic member (400). In addition, the VCM (600) may furtherinclude a cover can (500).

The stator (100) includes a first driving unit (120) and a housing(150). The stator (100) generates a magnetic field for driving the rotor(200, described later). The first driving unit (120) may include a coilblock formed by winding a long wire insulated by an insulation resin ina cylindrical shape, for example. In a case a voltage having a voltagedifference is applied to the first driving unit (120) including the coilblock formed by winding a long wire insulated by an insulation resin ina cylindrical shape, a first magnetic field is generated from the firstdriving unit (120) where a direction of the first driving unit (120) ischanged in response to a direction of a current flowing in the firstdriving unit (120).

Although the exemplary embodiment of the present disclosure hasillustrated and explained a case where the first driving unit (120) ofthe stator (100) is a coil block, the first driving unit (120) mayinclude a magnet capable of generating a magnetic field.

The housing (150) fixes the first driving unit (120). The housing (150)may include a housing body (152) and pillars (154), for example. Thehousing body (152) takes a shape of a rectangular plate, for example,and is centrally formed with an opening (153) exposing a lens mounted ona bobbin (described later). The housing body (152) is formed at an uppersurface thereof with a plurality of bosses (156) for fixing an elasticmember (described later). Each pillar (154) is protruded from eachcorner (four corners) of a bottom surface of the housing body (152)opposite to the base (300).

An inner surface of the first driving unit (120) including the coilblock is fixed to an outer surface of the pillars (154). The pillars(154) may be coupled to an upper surface of the base (300, describedlater).

The rotor (200) includes a bobbin (210) and a second driving unit (250).The rotor (200) moves relative to the stator (100) to adjust a gapbetween an image sensor (described later) arranged at a bottom surfaceof the base (300, described later) and a lens (205).

The bobbin (210) takes a shape of a cylinder formed with a hollow hole,and is formed at an inner surface thereof with a screw thread for fixingthe lens (205). The bobbin (210) is formed at an outer surface thereofwith flat fixtures (215) for fixing each of the second driving unit(250). For a non-limiting example, four fixtures (215) are formed at theouter surface of the bobbin (210) each at an equi-distance.

Each of the second driving units (250) may include a magnet generating asecond magnetic field, each having a plate shape, for example, and befixed to each fixture (215) formed at the outer surface of the bobbin(215). Each second driving unit (250) may be attached to the fixture(215) using an adhesive. Each of the second driving units (250) isopposite to the first driving unit (120) of the stator (100).

Although the exemplary embodiment of the present disclosure hasillustrated and explained a case where the second driving unit (250) isa magnet, the second driving unit (250) may alternatively include a coilblock formed by winding an insulated long wire.

In a non-limiting example, in a case the first driving unit includes acoil block, the second driving unit (250) includes a magnet, andalternatively in a case the first driving unit (120) includes a magnet,the second driving unit includes a coil block. The rotor (200)horizontally moves based on the base (300) in response to an attractiveforce and a repulsive force generated by the first magnetic fieldgenerated by the first driving unit (120) and generated by the secondmagnetic field generated by the second driving unit (250).

Meanwhile, in the exemplary embodiment of the present disclosure, therotor (200) is distanced from an upper surface of the base (300) in astate where a driving signal is not applied to the first driving unit(120) or the second driving unit (250).

The base (300) takes a shape of a cubic plate to fix the stator (100).The base (300) is centrally formed with an opening for passing lighthaving passed the lens (205) embedded in the bobbin (210) of the rotor(200). Each of the four corners of the upper surface (320) of theplate-shaped base (300) is formed with a coupling pillar (325), wherethe coupling pillar (325) serves to couple the cover can (500) and thebase (300).

The base (300) is fixed at a rear surface thereof by an IR (Infrared)filter (301) generating an image corresponding to the light havingpassed the lens (205) of the bobbin (210) and an image sensor (notdescribed). Meanwhile, the upper surface (320) of the plate-shaped base(300) is formed with a bobbin accommodation groove (330) concavelyformed from the upper surface (320) of the base (300), where the bobbinaccommodation groove (330) functions to accommodate a bottom surface ofthe bobbin (210).

The bobbin accommodation groove (330) is greater than an area of thebobbin (210), and the bobbin (210) and the base (300) may be partiallyoverlapped by the bobbin accommodation groove (330). In the exemplaryembodiment of the present disclosure, depth of the bobbin accommodationgroove (330) may be formed in consideration of a stroke length of therotor (200).

Meanwhile, a floor surface (335) of the base (300) formed by the bobbinaccommodation groove (330) is arranged with a shock absorption member(350) formed along the opening (310) of the base (300). The shockabsorption member (350) absorbs shock and vibration generated bycollision between the bobbin (210) and the floor surface (335) of thebase (300), for example. In the exemplary embodiment of the presentdisclosure, the shock absorption member (350) may include any oneselected from a group consisting of a sponge, a synthetic resin havingelasticity and a rubber. The shock absorption member (350) may be formedin the shape of a circular plate having a thin thickness.

In the exemplary embodiment of the present disclosure, the rotor (200)is distanced from the upper surface of the base (300) by the elasticmember (400) while no driving signal is applied to the first drivingunit (120) of the stator (100) and the second driving unit (250) of therotor (200).

In a case the rotor (200) is distanced from the upper surface of thebase (300) by the elastic member (400) while no driving signal isapplied to the first driving unit (120) of the stator (100) and thesecond driving unit (250) of the rotor (200), the rotor (200) moves to adirection distancing from the upper surface of the base (300) or to adirection approaching the upper surface of the base (300) as the drivingsignal is applied to any one of the first driving unit (120) of thestator (100) or the second driving unit (250) of the rotor (200),whereby intensity of current and power consumption required for drivingthe rotor (200) can be greatly reduced.

The elastic member (400) for distancing the rotor (200) from the uppersurface of the base (300) includes a first elastic member (440) and asecond elastic member (450). The elastic member (400) serves to distancethe bottom surface of the bobbin (210) from the floor surface (335)formed by the bobbin accommodation groove (330) formed on the uppersurface (320) of the base (300), in a case no driving signal is appliedto the second driving unit (250).

The first elastic member (440) elastically supports the bottom surfaceof the bobbin (210) of the rotor (200), and serves to float the bottomsurface of the bobbin (210) of the rotor (200) to an upper surface ofthe bobbin accommodation groove (330) of the base (300). The firstelastic member (440) includes a first inner elastic unit (410), a firstouter elastic unit (420) and a first connection elastic unit (430).

The first inner elastic unit (410) is formed in a shape of a circularring, for example, and is coupled to the bottom surface or a bottom endof the bobbin (210). The first inner elastic unit (410) is coupled tothe bottom surface of the bobbin (210) using an adhesive orthermosetting method, for example. The first inner elastic unit (410),being coupled to the bottom surface of the bobbin (210), is formed witha size insertable into the bobbin accommodation groove (330) of the base(300).

The first outer elastic unit (420) is arranged at an outer side of thefirst inner elastic unit (410) and takes a shape of a square frame. Thefirst outer elastic unit (420) is formed with a size larger than thebobbin accommodation groove (330) of the base (300), such that the firstouter elastic unit (420) is arranged on the upper surface (320) of thebase (300). The first outer elastic unit (420) may be fixed on the uppersurface (320) of the base (300) by the pillars (154) of the housing(150) at the stator (100), for example.

The first connection elastic unit (430) elastically connects the firstinner elastic unit (410) and the first outer elastic unit (420), wherethe first inner elastic unit (410) comes to possess elasticity by thefirst connection elastic unit (430). The first connection elastic unit(430) has a first spring constant (K), where the first spring constant(K) may be changed by shape, thickness, length and dimension of thefirst connection elastic unit (430).

Although the exemplary embodiment of the present disclosure hasillustrated and explained one first elastic member (440), alternatively,the first elastic member (440) may be coupled to the bottom surface ofthe base (300) in a pair, each being symmetrical to the other.

The second elastic member (450) is coupled to a coupling boss (156)formed on an upper surface of the housing body (152) of the housing(150) at the stator (100). The second elastic member (450) includes asecond inner elastic unit (451), a second outer elastic unit (452) and asecond connection elastic unit (453).

The second inner elastic unit (451) is coupled to the upper surface ofan upper end of the bobbin (210). The second outer elastic unit (452) isarranged on an upper surface of the housing body (152). The secondconnection elastic unit (453) serves to connect the second inner elasticunit (451) and the second outer elastic unit (452) and possesses asecond spring constant (K). The second spring constant (K) of the secondconnection elastic unit (453) may be changed by shape, thickness, lengthand dimension of the second connection elastic unit (453).

The second outer elastic unit (452) arranged on the upper surface of thehousing body (152) is formed with a coupling hole (455) coupled to acoupling boss (156) formed on the upper surface of the housing body(152).

Referring to FIG. 1 again, the VCM (600) may further include a cover can(500). The cover can (500) includes an upper plate (510) formed with anopening exposing the lens (205) of the rotor (200), and a lateral plate(520) extended to a direction facing the base (300) from an edge of theupper plate (510), where the lateral plate (520) is coupled to a lateralsurface of the base (300).

Referring to FIG. 1 again, the bobbin (210) of the rotor (200) accordingto an exemplary embodiment of the present disclosure may be driven to afirst direction (FD) distancing from the upper surface (320) of the base(300) by a force generated by the first and second driving units (120,250), and a second direction (SD) facing a floor surface of the bobbinaccommodation groove (330) of the base (300) in an opposite directionfrom the first direction (FD). The bobbin (210) of the rotor (200)according to an exemplary embodiment of the present disclosure is drivento the first direction (FD), in a case a forward current is applied tothe first driving unit (120), and to the second direction (SD) in anopposite direction of the first direction (FD), in a case a reversecurrent opposite to the forward current is applied to the first drivingunit (120).

At this time, the forward current or reverse current applied to thefirst driving unit (120) may be realized by adjusting a voltagedifference applied to distal ends of the first driving unit (120). Therotor (200) of the VCM (600) illustrated in FIGS. 1, 2 and 3 is arrangedto a direction perpendicular to a ground surface without tilting, in astate the optical axis of the lens (205) is arranged perpendicular tothe ground surface (or on a horizontal surface of the ground surface),that is, the VCM (600) lies flat (or on a horizontal surface of) to theground surface.

However, the VCM (600) may be arranged in various directions, in a casea user photographs an object using a smart phone mounted with the VCM(600). In a non-limiting example, in a case the optical axis of the lens(205) mounted on the rotor (200) of the VCM (600) is arranged to face adirection parallel with the ground surface (or horizontal surface), therotor (200) is applied with a moment in response to the gravity centerof the rotor (200) and gravity, whereby the rotor (200) may be generatedwith a tilt.

In the exemplary embodiment of the present disclosure, the VCM (600)restricts or inhibits the tilt of the rotor (200) generated by change inposture or change in arrangement based on a reference surface (groundsurface or horizontal surface).

In order to restrict or inhibit the tilt of the rotor (200) generated bychange in posture or change in arrangement, each of the first and secondelastic members (440, 450) of the elastic member (400) elasticallysupporting the rotor (200) has a mutually different spring constant (K)relative to the gravity center of the rotor (200).

Although the exemplary embodiment of the present disclosure hasillustrated and explained that each of the first and second elasticmembers (440, 450) of the elastic member (400) elastically supportingthe rotor (200) has a mutually different spring constant (K) relative tothe gravity center of the rotor (200), it should be apparent to theskilled in the art that each of the first and second elastic members(440, 450) of the elastic member (400) elastically supporting the rotor(200) has a mutually different elastic modulus (E) relative to thegravity center of the rotor (200).

FIG. 4 is a cross-sectional view illustrating a VCM based on acomparative example in contrast to the VCM according to the firstexemplary embodiment of the present disclosure.

Referring to FIG. 4, a rotor (200 a) is coupled to a stator (100 a) byelastic members (440 a, 450 a, 400 a), and the rotor (200 a) isdistanced from an upper surface of a base (300 a), in a case no drivingsignal is applied. In the comparative example, the first elastic member(440 a) and the second elastic member (450 a) of the elastic member (400a) have the same spring constant (K) and same elastic modulus (E).Furthermore, in the comparative example, a gravity center (G) of therotor (200 a) is formed at a position distanced as much as a length (L1)toward an upper end of the rotor (200 a) based on a center (C) of therotor (200 a).

In the comparative example, in a case an optical axis of the rotor (200a) of the VCM (600 a) is arranged in parallel with the ground surface,that is, in a case the elastic member (400 a) is arranged to a seconddirection (SD) which is perpendicular to the ground surface, the gravitycenter (G) of the rotor (200 a) is generated with a moment (M) byself-weight of the rotor (200 a), where the rotor (200 a) is tilted bythe moment (M) generated to a clockwise direction.

In the comparative example, the tilting of the rotor (200 a) inhibits anoptical axis of a lens from being in line with an optical axis of animage sensor, whereby a serious image defects may be generated.

FIG. 5 is a cross-sectional view illustrating the VCM in contrast to thecomparative example of FIG. 4 according to the first exemplaryembodiment of the present disclosure.

Referring to FIG. 5, a rotor (200) is coupled to a stator (100) byelastic members (440, 450, 400), where the rotor is distanced from anupper surface of the base (300 a), in a case no driving signal isapplied. Each of the first and second elastic members (440, 450) of theelastic member (400) has a mutually different spring constant (K).Furthermore, a gravity center (G) of the rotor (200) is formed at aposition distanced as much as a length (L1) toward an upper end of therotor (200) based on a center (C) of the rotor (200 a).

Although the gravity center (G) of the rotor (200) is generated with amoment (M) by self-weight of the rotor (200), in a case an optical axisof the rotor (200) of the VCM (600) is arranged in parallel with theground surface, that is, in a case the elastic member (400 a) isarranged to a second direction (SD) which is perpendicular to the groundsurface, the rotor (200) is not generated in an exemplary embodiment ofthe present disclosure with a tilt by the moment unlike the comparativeexample of FIG. 4. This is because each of the first and second elasticmembers (440, 450) of the elastic member (400) has a mutually differentspring constant (K) as explained before.

To be more specific, in a case the gravity center (G) of the rotor (200)is formed close to the second elastic member (450) based on the center(C) of the rotor (200), the first elastic member (440) has the firstspring constant (K1), whereas the second elastic member (450) has asecond spring constant (K2) greater than the first spring constant (K1)of the first elastic member (440) in order to inhibit the rotor frombeing tilted through compensation of moment.

The second spring constant (K2) in the exemplary embodiment of thepresent disclosure has an appropriate value adequate to compensate themoment capable of tilting the rotor (200), whereby the second springconstant (K2) may increase in proportion to the length (L1) between thecenter (C) of the rotor (200) and the gravity center (G) of the rotor(200). Alternatively, it should be apparent that the first springconstant (K1) of the first elastic member (440) may decrease in reverseproportion to the second spring constant (K2).

The first elastic member (440) may be formed with a first area, and thesecond elastic member (450) may be formed with a second area, in orderto allow the first elastic member (440) to have the first springconstant (K1), and the second elastic member (450) to have a secondspring constant (K2) greater than the first spring constant (K1) of thefirst elastic member (440).

Furthermore, the first connection elastic unit (430) of the firstelastic member (440) is formed with a first length, and the secondconnection elastic unit (453) of the second elastic member (450) isformed with a second length longer than the first length to allow thefirst elastic member (440) to have the first spring constant (K1), andthe second elastic member (450) to have a second spring constant (K2)greater than the first spring constant (K1) of the first elastic member(440).

Still furthermore, the first connection elastic unit (430) of the firstelastic member (440) and the second connection elastic unit (453) of thesecond elastic member (450) may be formed with a mutually differentshape to allow the first elastic member (440) to have the first springconstant (K1), and the second elastic member (450) to have a secondspring constant (K2) greater than the first spring constant (K1) of thefirst elastic member (440).

FIG. 6 is a cross-sectional view illustrating a VCM based on a secondcomparative example in contrast to the VCM according to the firstexemplary embodiment of the present disclosure.

Referring to FIG. 6, a rotor (200 b) is coupled to a stator (100 b) byelastic members (440 b, 450 b, 400 b), where the rotor (200 b) isdistanced from an upper surface of a base (300 b), in a case no drivingsignal is applied.

Each of the first elastic member (440 b) and the second elastic member(450 b) of the elastic member (400 b) in the second comparative examplehas a same elastic modulus (E) and same spring constant (K).Furthermore, a gravity center (G) of the rotor (200 b) is formed at aposition distanced as much as a length (L1) toward an upper end of therotor (200 b) based on a center (C) of the rotor (200 b) in the secondcomparative example.

In the second comparative example, in a case an optical axis of therotor (200 b) of the VCM (600 b) is arranged in parallel with the groundsurface, that is, in a case the elastic member (400 b) is arranged to asecond direction (SD) which is perpendicular to the ground surface, thegravity center (G) of the rotor (200 b) is generated with a moment (M)by self-weight of the rotor (200 b), where the rotor (200 b) is tiltedby the moment (M) generated to a counterclockwise direction.

In the second comparative example, the tilting of the rotor (200 b)inhibits an optical axis of a lens from being in line with an opticalaxis of an image sensor, whereby a serious image defects may begenerated due to the rotor (200 b) being tilted to a counterclockwisedirection.

FIG. 7 is a cross-sectional view illustrating a VCM based on the secondcomparative example of FIG. 6 in contrast to the VCM according to thefirst exemplary embodiment of the present disclosure.

Referring to FIG. 7, a rotor (200) is coupled to a stator (100) byelastic members (440, 450, 400), where the rotor (200) is distanced froman upper surface of a base (300), in a case no driving signal isapplied.

Each of the first elastic member (440) and the second elastic member(450) of the elastic member (400) has a mutually different springconstant (K). Furthermore, a gravity center (G) of the rotor (200) isformed at a position distanced as much as a length (L1) toward a bottomend of the rotor (200) based on a center (C) of the rotor (200 b) as inthe second comparative example.

In a case an optical axis of the rotor (200) of the VCM (600) isarranged in parallel with the ground surface, that is, in a case theelastic member (400) is arranged to a second direction (SD) which isperpendicular to the ground surface, the gravity center (G) of the rotor(200) is generated with a moment (M) by self-weight of the rotor (200),but no tilt is generated with the rotor (200) unlike the comparativeexample of FIG. 6.

This is because each of the first and second elastic members (440, 450)of the elastic member (400) has a mutually different spring constant (K)as explained before in order to inhibit the rotor (200) from beingtilted by the gravity center (G) of the rotor (200).

To be more specific, in a case the gravity center (G) of the rotor (200)is formed close to the second elastic member (450) based on the center(C) of the rotor (200), the second elastic member (450) has the firstspring constant (K1), whereas the first elastic member (440) has asecond spring constant (K2) greater than the first spring constant (K1)of the second elastic member (450) in order to inhibit the rotor frombeing tilted through compensation of moment.

The second spring constant (K2) of the first elastic member (440) in theexemplary embodiment of the present disclosure has an appropriate valueadequate to compensate the moment (M) capable of tilting the rotor(200), whereby the second spring constant (K2) may increase inproportion to the length (L1) between the center (C) of the rotor (200)and the gravity center (G) of the rotor (200). Alternatively, it shouldbe apparent that the first spring constant (K1) of the second elasticmember (450) may decrease in reverse proportion to the second springconstant (K2).

The first elastic member (440) may be formed with a first area, and thesecond elastic member (450) may be formed with a second area smallerthan the first area, in order to allow the second elastic member (450)to have the first spring constant (K1), and the first elastic member(440) to have a second spring constant (K2) greater than the firstspring constant (K1).

Furthermore, the first connection elastic unit (430) of the firstelastic member (440) is formed with a first length, and the secondconnection elastic unit (453) of the second elastic member (450) isformed with a second length longer than the first length to allow thefirst elastic member (440) to have the first spring constant (K1), andthe second elastic member (450) to have a second spring constant (K2)greater than the first spring constant (K1).

Still furthermore, the first connection elastic unit (430) of the firstelastic member (440) and the second connection elastic unit (453) of thesecond elastic member (450) may be formed with a mutually differentshape to allow the second elastic member (450) to have the first springconstant (K1), and the first elastic member (440) to have a secondspring constant (K2) greater than the first spring constant (K1).

Although the abovementioned description has disclosed a technicalcharacteristic in which the spring constant (K) of the first and secondelastic members (440, 450) coupled to an upper end and a bottom end ofthe rotor is individually adjusted in order to inhibit the rotor frombeing tilted, alternatively it should be apparent that the elasticmodulus (E) intrinsic to the first and second elastic members (440, 450)may be changed to inhibit the rotor from being tilted.

As apparent from the foregoing, the VCM according to the presentdisclosure has an is advantageous effect in that a bobbin mounted with alens is floated from a bobbin accommodation groove formed on an uppersurface of a base mounted with an image sensor to bi-directionally drivethe rotor to a direction distancing from the base or to a directionapproaching the base, whereby the VCM can be driven with a low current,and whereby power consumption can be reduced to adjust a focus betweenthe lens and the image sensor within a quick time, and whereby a contactnoise caused by driving of the bobbin can be reduced, and whereby therotor is inhibited from being tilted by a gravity center of the rotordistanced from the base to enhance the quality of an image.

Second Exemplary Embodiment

FIG. 8 is a schematic cross-sectional view illustrating a VCM accordingto a second exemplary embodiment of the present disclosure.

Referring to FIGS. 1, 2 and 8, a voice coil motor (hereinafter referredto as VCM, 600) may include a stator (100), a rotor (200), a base (300)and an elastic member (400). In addition, the VCM (600) may furtherinclude a cover (500).

The stator (100) includes a coil block (120) and a housing (150). Thestator (100) generates a magnetic field for driving the rotor (200,described later). Alternatively, the stator (100) may include a magnetgenerating a magnetic field, and the housing (150).

The coil block (120) may be formed by winding a long wire insulated byan insulation resin in a cylindrical shape, for example. In a case avoltage having a voltage difference is applied to the coil block (120)formed by winding a long wire insulated by an insulation resin in acylindrical shape, a magnetic field is generated from the coil block(120) where a direction of the magnetic field is changed in response toa direction of a current flowing in the coil block (120).

The housing (150) fixes the coil block (120). The housing (150) mayinclude a housing body (152) and pillars (154), for example. The housingbody (152) takes a shape of a rectangular plate, for example, and iscentrally formed with an opening (153) exposing a lens mounted on abobbin (described later). The housing body (152) is formed at an uppersurface thereof with a plurality of bosses (156) for fixing an upperelastic member (described later). Each pillar (154) is protruded fromeach corner (four corners) of a bottom surface of the housing body (152)opposite to the base (300).

An inner surface of the coil block (120) is fixed to an outer surface ofthe pillars (154). The pillars (154) may be coupled to an upper surfaceof the base (300, described later).

The coil block (120), in a wound state of a cylinder shape, may beattached to the pillars (154) of the housing (150) using an adhesive, ormay be directly wound on the pillars (154) of the housing (150).

The rotor (200) includes a bobbin (210) and a magnet (250). In a casethe stator (100) includes the coil block (120) in the exemplaryembodiment of the present disclosure, the rotor (200) includes themagnet (250), and in a case the stator includes the magnet, the rotor(200) includes the coil block.

The rotor (200) is driven to a first direction approaching the base(300), or to a second direction distancing from the base (300). Thebobbin (210) is fixed by a cylinder-shaped lens (205). The rotor (200)moves relative to the stator (100) to adjust a gap between an imagesensor (described later) arranged at a bottom surface of the base (300,described later) and a lens (205).

The bobbin (210) takes a shape of a cylinder formed with a hollow hole,for example, and is formed at an inner surface thereof with a screwthread for fixing the lens (205). The bobbin (210) is formed at an outersurface thereof with magnet fixtures (215) for fixing a plurality ofmagnets (250). For a non-limiting example, four magnet fixtures (215)are formed at the outer surface of the bobbin (210), each at anequi-distance.

Each of the magnets (250) may take a shape of a plate, for example, andbe fixed to each magnet fixture (215) formed at the outer surface of thebobbin (210). Each magnet (250) may be attached to the magnet fixture(215) using an adhesive. Each of the magnets (250) is arranged oppositeto the coil block (120) of the stator (100).

The base (300) takes a shape of a cubic plate, for example, to fix thestator (100). The base (300) is centrally formed with an opening forpassing light having passed the lens (205) embedded in the bobbin (210)of the rotor (200). Each of the four corners of an upper surface (320)of the plate-shaped base (300) is formed with coupling pillars (325),where each of the coupling pillar (325) serves to couple the cover (500,described later) and the base (300).

The base (300) is fixed at a rear surface thereof by an IR (Infrared)filter (301) generating an image corresponding to the light havingpassed the lens (205) of the bobbin (210) and an image sensor (notdescribed). Meanwhile, the upper surface (320) of the plate-shaped base(300) is formed with a bobbin accommodation groove (330) concavelyformed from the upper surface (320) of the base (300), where the bobbinaccommodation groove (330) functions to accommodate a bottom surface ofthe bobbin (210).

The bobbin accommodation groove (330) is greater than an area of thebobbin (210), and the bobbin (210) and the base (300) may be partiallyoverlapped by the bobbin accommodation groove (330). In the exemplaryembodiment of the present disclosure, depth of the bobbin accommodationgroove (330) may be formed in consideration of a stroke length of therotor (200).

Meanwhile, a floor surface (335) of the base (300) formed by the bobbinaccommodation groove (330) is arranged with a shock absorption member(350) formed along the opening (310) of the base (300). The shockabsorption member (350) absorbs shock generated by collision between thebobbin (210) and the floor surface (335) of the base (300), for example.In the exemplary embodiment of the present disclosure, the shockabsorption member (350) may include any one selected from a groupconsisting of a sponge, a synthetic resin having elasticity and arubber. The shock absorption member (350) may be formed in the shape ofa circular plate having a thin thickness.

A first elastic member (440) of an elastic member (400) elasticallysupports the bobbin (210) of the rotor (200), and serves to float thebottom surface of the bobbin (210) of the rotor (200) to an uppersurface of the bobbin accommodation groove (330) of the base (300).

That is, the first elastic member (440) forms a gap between the bottomsurface of the bobbin (210) and a floor surface (335) formed by thebobbin accommodation groove (330) formed on the upper surface (320) ofthe base (300) regardless of posture of the bobbin (210), in a case nocurrent is applied to the coil block (120). At this time, the posture ofthe bobbin (210) means that the lens of the bobbin (210) facesdownwards, faces upwards or is arranged in parallel with a groundsurface.

The first elastic member (440) includes a first inner elastic unit(410), a first outer elastic unit (420) and a first connection elasticunit (430).

The first inner elastic unit (410) is formed in a shape of a circularring, for example, and is coupled to the bottom surface or a bottom endof the bobbin (210). The first inner elastic unit (410) is coupled tothe bottom surface of the bobbin (210) using an adhesive orthermosetting method, for example. The first inner elastic unit (410),being coupled to the bottom surface of the bobbin (210), is formed witha size insertable into the bobbin accommodation groove (330) of the base(300).

The first outer elastic unit (420) is arranged at an outer side of thefirst inner elastic unit (410) and takes a shape of a square frame. Thefirst outer elastic unit (420) is formed with a size larger than thebobbin accommodation groove (330) of the base (300), such that the firstouter elastic unit (420) is arranged on the upper surface (320) of thebase (300). The first outer elastic unit (420) may be fixed on the uppersurface (320) of the base (300) by the pillars (154) of the housing(150) at the stator (100), for example.

The first connection elastic unit (430) elastically connects the firstinner elastic unit (410) and the first outer elastic unit (420), wherethe first inner elastic unit (410) comes to possess elasticity by thefirst connection elastic unit (430).

The bobbin (210) in an exemplary embodiment of the present disclosure isfloated on an upper surface of the bobbin accommodation groove (330) ofthe base (300) by the first elastic member (440).

The first inner elastic unit (410) is distanced from a floor surface(335) formed by the bobbin accommodation groove (330), and the firstinner elastic unit (410), the first outer elastic unit (420), and thefirst connection elastic unit (430) may be arranged on a same planarsurface, in a case no driving signal is applied to the coil block (120).Alternatively, the first inner elastic unit (410) may be arranged at aposition a bit lower than that of the first outer elastic unit (420), ina case no driving signal is applied to the coil block (120).

In an exemplary embodiment of the present disclosure, formation of thebobbin accommodation groove (330) concavely formed on the upper surface(320) of the base (300) may reduce an entire volume of the VCM (600),where the rotor (200) can be driven to a first direction facing the base(300), or to a direction distancing from the base (300). That is, therotor (200), in case of being distanced from the upper surface (320) ofthe base (300), may be driven to the first direction facing the base(300), or to the direction distancing from the base (300) in response tochanges in direction of a current applied to the coil block (120).

A coupling boss (156) formed on an upper surface of the housing body(152) of the housing (150) is coupled by a second elastic member (450).The second elastic member (450) includes a second inner elastic unit(451), a second outer elastic unit (452) and a second connection elasticunit (453).

The second inner elastic unit (451) is coupled to the upper surface ofthe bobbin (210). The second outer elastic unit (452) is arranged on anupper surface of the housing body (152). The second connection elasticunit (453) serves to connect the second inner elastic unit (451) and thesecond outer elastic unit (452). The second outer elastic unit (452)arranged on the upper surface of the housing body (152) is formed with acoupling hole (455) coupling with a coupling boss (156) formed on theupper surface of the housing body (152).

Referring to FIG. 1 again, the VCM (600) may further include a cover(500). The cover can (500) includes an upper plate (510) formed with anopening exposing the lens (205) of the rotor (200), and a lateral plate(520) extended to a direction facing the base (300) from an edge of theupper plate (510), where the lateral plate (520) is coupled to a lateralsurface of the base (300).

Referring to FIG. 2 again, the bobbin (210) of the rotor (200) accordingto an exemplary embodiment of the present disclosure may be driven to afirst direction facing the upper surface (320) of the base (300) and asecond direction distancing from the base (300) in an opposite directionfrom the first direction in response to a force generated by the coilblock (120) and the magnet (250). A forward current or a backwardcurrent applied to the coil block (120) may be realized by adjusting avoltage difference applied to both ends of the coil block (120).

FIG. 9 is a graph illustrating a current-distance characteristic and acurrent-tilt amount characteristic of a rotor of FIG. 8.

Referring to FIGS. 8 and 9, a voice coil motor (hereinafter referred toas VCM, 600) may include a stator (100), a rotor (200), a base (300), anelastic member (400), and a cover (500).

The base (300) takes a shape of a plate and is centrally formed with anopening for passing light, where the base (300) functions as a bottomstopper of the rotor (200). The base (300) may be formed at an uppersurface with an accommodation groove accommodating a bottom surface ofthe rotor (200) for distancing an upper surface of the base (300) from abottom surface of the rotor (200). The base (300) is formed at the uppersurface with a shock absorption member (350) inhibiting noise generatedby collision between the rotor (200) and the base (300). In theexemplary embodiment of the present disclosure, the shock absorptionmember (350) may include any one selected from a group consisting of asponge, a synthetic resin having elasticity and a rubber.

The base (300) may be arranged at a rear surface of a rear end with animage sensor (1) which in turn changes a light incident from the rotor(200) to a digital image or a video. The stator (100) is secured on thebase (300), includes a coil block (120) which is a first driving unitfor generating a magnetic field, and is formed therein with anaccommodation space.

The coil block (120) which is a first driving unit a coil formed bywinding a long wire insulated by an insulation resin in a cylindricalshape for generating a magnetic field in response to a current. Therotor (200) is arranged inside the stator (100), and includes a lens(205). The rotor (200) is mounted at an outer surface thereof with amagnet including a second driving unit generating a magnetic field.

In an exemplary embodiment of the present disclosure, in a case thefirst driving unit of the stator (100) includes the coil block (120),the second driving unit of the rotor (200) may include a magnet (250).Alternatively, the first driving unit of the stator (100) may include amagnet, and the second driving unit may include a coil block, in a casethe first driving unit of the stator (100) includes a magnet.

An elastic member (400) is fixed at one side thereof to the rotor (200),and is fixed at the other side opposite to the one side to the stator(100), and elastically supports the rotor (200). The elastic member(400) in an exemplary embodiment of the present disclosure may include afirst elastic member (440) formed at a bottom end of an outer surface ofthe rotor (200) and a second elastic member (450) formed at an upper endof the outer surface of the rotor (200). The first and second elasticmembers (440, 450) comprising the elastic member (400) is distanced fromthe upper surface of the base (300), in a case no power is applied tothe coil block (120) of the stator (100), where no offset (staircasesill) is formed on the first and second elastic members (440, 450).

The elastic member (400) distances the rotor (200) from the uppersurface of the base (300), in a case no driving signal is applied to thecoil block (120) generating a magnetic field.

The cover (500) is secured to the base (300), and wraps the stator (100)and the rotor (200). The cover (500) also serves as an upper stopperstopping the rotor (200). The cover (500) is arranged with a shockabsorption member (350) inhibiting noise generated by collision betweenthe rotor (200) and the cover (500). In the exemplary embodiment of thepresent disclosure, the shock absorption member (350) may include anyone selected from a group consisting of a sponge, a synthetic resinhaving elasticity and a rubber.

Referring to FIGS. 8 and 9 again, the rotor (200) of the VCM (600) movesbetween an upper surface of the base (300) and an inner surface of thecover (500) in response to a current applied to the coil block (120).

Hereinafter, a gap between the upper surface of the base (300) acting asa bottom stopper of the rotor (200) of the VCM (600) and the innersurface of the cover (500) acting as an upper stopper of the rotor (200)is defined as a ‘moving section’.

That is, the moving section may be defined as a section between acontact surface between the rotor (200) and the base (300) and a contactsurface between the rotor (200) and the cover (500).

In order to realize a particular focus on the image sensor (1) bydriving the rotor (200) of the VCM (600) illustrated in FIG. 9, aninitial driving signal (S) of 0 [mA] to a driving signal of A [mA] mustbe first applied to the coil block (120) of the stator (100), wherebythe rotor (200) moves to a first direction facing the upper surface ofthe base (300) and contacts the upper surface of the base (300). Afterthe rotor (200) is brought into contact with the upper surface of thebase (300), the coil block (120) which is the first driving unit of therotor (200) is in turn provided with a current continuously increasingless than from A [mA] to B [mA].

However, even if a current continuously increasing less than from A [mA]to B [mA] is continuously provided, the rotor (200) is not distancedfrom the upper surface of the base (300). This is because anelectromagnetic force acting between the coil block (120) of the firstdriving unit and the magnet of second driving unit is smaller than anelastic force of the elastic member (400) and/or a self-weight of therotor (200), in a case a current less than B [mA] is applied to the coilblock (120) of the first driving unit at the stator (100).

Meanwhile, with reference to a tilt graph of the rotor (200) indicatedin a solid line of FIG. 10, the rotor (200) is generated with a severetrembling or a tilt, in a case a current continuously increasing lessthan from A [mA] to B [mA] is continuously provided to the coil block(120) of the stator (100). The trembling or a tilt of the rotor (200) isgreatest, in a case a current is larger than B [mA] and less than C[mA].

However, the rotor (200) is not generated with trembling or a tilt, in acase a current is larger than C [mA] is applied to the coil block (120)which is a first driving unit. Thus, a current applied to the coil block(120) corresponding to a section where an unstable tilt is generated tothe rotor (200) is a current between A [mA] and C [mA], in a case aninfinite focus is formed in the exemplary embodiment of the presentdisclosure.

The rotor (200) is brought into contact (D) with the upper surface ofthe base (300), in a case a current less than A [mA] to B [mA] isapplied to the coil block (120) of the stator (100). The rotor (200) isdistanced from the upper surface of the base (300) to be positioned atan E position, which is a distance axis of the graph, in a case acurrent smaller than C [mA] is applied to the coil block (120) which isthe first driving unit.

Now, in an exemplary embodiment of the present disclosure, a D-E sectionwhich generates a trembling or a tilt of the rotor (200) is defined asan “ineffective focus section”, and a section above E section where notrembling or tilt of the rotor (200) is generated as an “effective focussection”. The effective focus section is formed in the moving section ofthe rotor (200), while the ineffective focus section is formed at bothsides of the effective focus section.

In a case a particular focus, e g., an infinite focus, is formed insidethe ineffective focus section, a severe trembling or tilt may begenerated from the rotor (200) when photographing an object in aninfinite focus, such that in the exemplary embodiment of the presentdisclosure, no focusing operation is performed in the ineffective focussection, and a focusing operation is performed at an effective focussection above E section in the graph.

In the exemplary embodiment of the present disclosure, the infinitefocus is not formed at the ineffective focus section but formed at theeffective focus section. In the exemplary embodiment of the presentdisclosure, the ineffective focus section where trembling or tilt isgenerated from the rotor (200) may start from a position distancedapproximately 5 μm˜20 μm from the upper surface of the base (300), forexample.

Furthermore, the infinite focus in the exemplary embodiment of thepresent disclosure is formed at a position distanced approximately 10 μmfrom the upper surface of the base (300), whereby no trembling or tiltof the rotor (200) can be generated to form an infinite focus.

Meanwhile, because the ineffective focus section, where trembling ortilt of the rotor (200) can be generated as in the infinite focus,reaches down to a place spaced apart at a predetermined distance from aninner surface of the cover (500) during formation of diopter (close-up)focus, the diopter focus is formed at an effective focus sectiondistanced approximately 5 μm˜20 μm from the inner surface of the cover(500) opposite to the lens (205).

In a case the rotor (200) reaches a position forming the diopter focusin the exemplary embodiment of the present disclosure, a current F [mA]applied to the coil block (120) may be approximately 20 [mA], forexample.

Conclusively, the effective focus section in the exemplary embodiment ofthe present disclosure exists within the moving section of the rotor(200), the effective focus section is formed at a position distancedapproximately 5 μm˜20 μm from the upper surface of the base (300), andthe effective focus section is coupled to the base (300) and formed at aposition distanced approximately 5 μm˜20 μm from the inner surface ofthe cover (500) wrapping the stator (100) and the rotor (200).

Furthermore, a distal end of the effective focus section adjacent to thebase (300) is formed with an infinite focus, and a distal end of theeffective focus section adjacent to the cover (500) is formed with adiopter (close-up) focus.

Although the exemplary embodiment of the present disclosure hasillustrated and explained that the first driving unit of the stator(100) includes the coil block (120), and the second driving unit of therotor (200) is a magnet (250), it should be alternatively apparent thatthe first driving unit of the stator (100) includes the magnet (250),and the second driving unit of the rotor (200) includes the coil block(120).

Meanwhile, a tilt amount of the rotor (200) at the effective focussection and the ineffective focus section is changed in response to acurrent amount applied to the coil block (120), and trembling amountand/or tilt amount of the rotor (200) in the effective focus sectionincluded in the moving section of the rotor (200) in the exemplaryembodiment of the present disclosure are/is within the moving section,and smaller than a trembling amount and/or tilt amount of the rotor(200) at the ineffective focus section formed at both sides of theeffective focus section.

Although the rotor (200) at the effective focus section in the exemplaryembodiment of the present disclosure possesses a minute (very small)trembling amount or a minute tilt amount, the tilt amount in theeffective focus section may be defined as substantially nil (zero),because the trembling amount and/or tilt amount of the rotor (200) inthe effective focus section is small enough as to be negligible comparedwith those and/or that in the ineffective focus section.

As apparent from the abovementioned description, no infinite focus ordiopter (close-up) focus is formed at an unstable section where thetrembling or tilt of the rotor is generated due to mixture ofelectromagnetic force and elastic force around the rotor, whereas theinfinite focus or diopter (close-up) focus is formed at a stable sectionwhere the trembling or tilt of the rotor is not generated to allow theimage sensor to generate a high quality image and video.

Third Exemplary Embodiment

FIG. 10 is a schematic cross-sectional view illustrating a VCM accordingto a third exemplary embodiment of the present disclosure, and FIG. 11is a graph illustrating a current-distance characteristic of a VCM ofFIG. 8.

Referring to FIGS. 1, 10 and 11, a voice coil motor (hereinafterreferred to as VCM, 600) may include a stator (100), a rotor (200), abase (300), an elastic member (400), and a cover (500).

The base (300) takes a shape of a plate and is centrally formed with anopening for passing light, where the base (300) functions as a bottomstopper of the rotor (200). The base (300) may be formed at an uppersurface with an accommodation groove accommodating a bottom surface ofthe rotor (200) for distancing an upper surface of the base (300) from abottom surface of the rotor (200). The base (300) is formed at the uppersurface with a shock absorption member (350) inhibiting noise generatedby collision between the rotor (200) and the base (300). In theexemplary embodiment of the present disclosure, the shock absorptionmember (350) may include any one selected from a group consisting of asponge, a synthetic resin having elasticity and a rubber.

The stator (100) is secured on the base (300), the stator (100) includesa first driving unit (120) for generating a magnetic field, and thestator (100) is formed therein with an accommodation space.

The first driving unit (120) may include a coil formed by winding a longwire insulated by an insulation resin in a cylindrical shape forgenerating a magnetic field in response to a current. Alternatively, thefirst driving unit (120) may include a magnet generating a magneticfield. In the exemplary embodiment of the present disclosure, the firstdriving unit (120) of the stator (100) may include a coil.

The rotor (200) is arranged inside the stator (100), and includes a lens(205). The rotor (200) is mounted at an outer surface thereof with asecond driving unit (250) generating a magnetic field.

In a case the first driving unit (120) of the stator (100) includes acoil, the second driving unit (250) of the rotor (200) may include amagnet. Alternatively, in a case the first driving unit (120) of thestator (100) includes a magnet, and the second driving unit (250) of therotor (200) may include a coil. In the exemplary embodiment of thepresent disclosure, the second driving unit (250) of the rotor (200)includes a magnet, for example.

An elastic member (400) is fixed at one side thereof to the rotor (200),and is fixed at the other side opposite to the one side to the stator(100), and elastically supports the rotor (200). The elastic member(400) may include a first elastic member (440) formed at a bottom end ofan outer surface of the rotor (200) and a second elastic member (450)formed at an upper end of the outer surface of the rotor (200). Theelastic member (400) distance the rotor (200) from the upper surface ofthe base (300), in a case no driving signal is applied to the firstdriving unit (120) of the stator (100) and the second driving unit (250)of the rotor (200)

The cover (500) is secured to the base (300), and wraps the stator (100)and the rotor (200). The cover (500) also serves as an upper stopperstopping the rotor (200). The cover (500) is arranged with a shockabsorption member (555) inhibiting noise generated by collision betweenthe rotor (200) and the cover (500). In the exemplary embodiment of thepresent disclosure, the shock absorption member (555) may include anyone selected from a group consisting of a sponge, a synthetic resinhaving elasticity and a rubber.

As a driving signal is applied to any one of the first driving unit(120) of the stator (100) and the second driving unit (250) of the rotor(200) while the rotor (200) is distanced from the upper surface of thebase (300) by the elastic member (400), the rotor (200) moves to adirection facing the base (300) or to a direction facing the cover(500), whereby a gap formed between the lens (205) arranged inside therotor (200) and the image sensor arranged at a rear side of the base(300) is adjusted to focus an outside light having passed the lens tothe image sensor.

Referring to FIGS. 10 and 11 again, in a case a driving signal is notapplied to the first driving unit (120) of the stator (100) or thesecond driving unit (250) of the rotor (200), a first stroke length(SD1) forming a bottom surface of the base (300) and the rotor (200) isshorter than a second stroke length (SD2) forming an upper surface ofthe cover (500) and the rotor (200). The reason of forming the firststroke length (SD1) shorter than the second stroke length (SD2) is thata user photographs a picture largely using an infinite focus of a cameramodule, and using a particular focus only at a particular occasion.

Referring to the graphs in FIG. 11, in order to realize an infinitefocus (1 m˜5 m of a distance to an object) frequently used by the imagesensor arranged at the rear side of the base (300) and the lens (205) ofthe rotor (200), the rotor (200) floated from the base (300) in astationary state is moved downwards facing the upper surface of the base(300) by the driving signal applied to the first driving unit (120) ofthe stator (100) or the second driving unit (250) of the rotor (200).The rotor (200) is first brought into contact with the upper surface ofthe base (300), which is to set a reference position for realizing aninfinite focus.

The distance between the bottom surface of the floated stationary rotor(200) and the upper surface of the base (300) is the first stroke length(SD1), and a current amount applied to the rotor (200) is C [mA], forexample, in order for the rotor (200) to contact the upper surface ofthe base (300).

Thereafter, in order realize an infinite focus between the lens (205)and the image sensor while the rotor (200) is brought into contact withthe upper surface of the base (300), the rotor (200) is in turn appliedwith a current of is D [mA] (where, D>C), whereby the rotor (200) isdistanced from the upper surface of the base (300) to move to aninfinite focus position. The rotor (200) on the infinite focus positionis distanced approximately 40 μm from the upper surface of the base, asin the previous comparative exemplary embodiment.

Meanwhile, in case of performing a diopter (close-up) photographing, thefirst driving unit (120) of the stator (100) or the second driving unit(250) of the rotor (200) is applied with a current of E [mA], and therotor (200) is brought into contact with the upper stopper which is thecover (500). At this time, a second stroke length (SD2) longer than thefirst stroke length (SD1) is formed between the upper surface of thefloated stationary rotor (200) and the cover (500), as illustrated inFIG. 10.

Referring to FIG. 11, the rotor (200) first descends towards the base(300) by approximately 100 μm in order to realize an infinite focusbetween the lens (205) and the image senor, and a current ofapproximately 9 [mA]˜10 [mA] is required in order to descend the rotor(200) by approximately 100 μm.

As a result, it is preferable that the first stroke length (SD1) betweenthe rotor (200) and the base (300) be shorter than the second strokelength (SD2) between the cover (500) and the rotor (200), in order torealize the rotor (200) using a low current and reduced powerconsumption during realization of infinite focus frequently used by auser. The second stroke length (SD2) may be twice or thrice larger thanthe first stroke length (SD1), based on the first stroke length (SD1).

Conversely, the first stroke length (SD1) between the rotor (200) andthe base (300) be longer than the second stroke length (SD2) between thecover (500) and the rotor (200), in order to realize the rotor (200)using a low current and reduced power consumption during realization ofdiopter (close-up) focus frequently used by a user.

That is, the first stroke length (SD1) between the rotor (200) and thebase (300) and the second stroke length (SD2) between the cover (500)and the rotor (200) may be differently formed in response to selectionor propensity of a user in the exemplary embodiment of the presentdisclosure.

Meanwhile, the first stroke length (SD1) between the rotor (200) and thebase (300) and the second stroke length (SD2) between the cover (500)and the rotor (200) may be changed in response to posture of the lens(205) of the VCM (600). In a non-limiting example, as illustrated inFIG.10, in a case the base (300) is arranged opposite to the groundsurface, the elastic member (400) droops towards the upper surface ofthe base (300) in response to the self-weight of the rotor (200),whereby the first stroke length (SD1) between the rotor (200) and thebase (300) decreases while the second stroke length (SD2) between thecover (500) and the rotor (200) increases. However, even in this case,the first stroke length (SD1) between the rotor (200) and the base (300)is shorter than the second stroke length (SD2) between the cover (500)and the rotor (200).

FIG. 12 is a cross-sectional view illustrating a state of a reversed VCMof FIG. 10.

Referring to FIG. 12, in a case the cover (500) is arranged opposite tothe ground surface, the elastic member (400) droops towards the cover(500) in response to the self-weight of the rotor (200), whereby thefirst stroke length (SD1) between the rotor (200) and the base (300)increases while the second stroke length (SD2) between the cover (500)and the rotor (200) decreases. However, even in this case, the firststroke length (SD1) between the rotor (200) and the base (300) isshorter than the second stroke length (SD2) between the cover (500) andthe rotor (200). That is, the first stroke length (SD1) is a lengthincluding the drooped length of the rotor (200).

FIG. 13 is a schematic cross-sectional view illustrating a VCM accordingto another exemplary embodiment of the present disclosure.

Referring to FIG. 13, a voice coil motor (hereinafter referred to asVCM, 600) may include a stator (100), a rotor (200), a base (300), anelastic member (400), and a cover (500).

The stator (100) is arranged on the base (300), and a rotor (200)coupled to a lens (205) is arranged on the base (300) corresponding toan interior of the stator (100). The elastic member (400) is coupled tothe stator (100) and the rotor (200) to allow the rotor (200) to floatfrom an upper surface of the base (300), in a case no driving signalsuch as a current is applied to the stator (100) and the rotor (200),and the cover (500) is coupled to the base (300).

Hereinafter, a position bisecting the upper surface and a bottom surfaceof the rotor (200) is defined as a first center part (230 a), and aposition bisecting a bottom surface of the cover (500) and the uppersurface of the base (300) is defined as a second center part (230 b).

In the exemplary embodiment of the present disclosure, in order torealize the low current and reduced power consumption characteristicsduring realization of infinite focus frequently used by a user, thefirst center part (230 a) which is a position bisecting the uppersurface and the bottom surface of the rotor (200) is located below thesecond center part (230 b) bisecting a bottom surface of the cover (500)and the upper surface of the base (300).

A first gap (G1) formed between the base (300) and the rotor (200) isnarrower than a second gap (G2) formed between the rotor (200) and thecover (500) by arranging the first center part (230 a) which is aposition bisecting the upper surface and the bottom surface of the rotor(200) below the second center part (230 b) bisecting a bottom surface ofthe cover (500) and the upper surface of the base (300).

Furthermore, the first gap (G1) formed between the base (300) and therotor (200) may be formed twice or thrice narrower than the second gap(G2) formed between the rotor (200) and the cover (500).

As apparent from the foregoing, the voice coil motor according to thepresent disclosure has an industrial adaptability in that a rotor isfloated from an upper surface of a base when a driving signal is notapplied, and a length of a stroke length or a gap between the floatedrotor and the upper surface of the base is differently formed from astroke length or a gap between the floated rotor and the cover torealize a low current consumption characteristic or a low powerconsumption characteristic.

The above-mentioned VCM according to the present disclosure may,however, be embodied in many different forms and should not be construedas limited to the embodiment set forth herein. Thus, it is intended thatembodiment of the present disclosure may cover the modifications andvariations of this disclosure provided they come within the scope of theappended claims and their equivalents. While particular features oraspects may have been disclosed with respect to several embodiments,such features or aspects may be selectively combined with one or moreother features and/or aspects of other embodiments as may be desired.

What is claimed is:
 1. A VCM, the VCM comprising: a stator including afirst driving unit; a rotor arranged inside the stator, including asecond driving unit responding to the first driving unit and mountedtherein with a lens; a base fixing the stator; and an elastic membercoupled to the rotor to float the rotor from the base in a case adriving signal for driving the first and second driving units is notapplied to the first and/or second driving units.
 2. The VCM of claim 1,wherein the rotor moves to a first direction facing the base or to asecond direction distancing from the base.
 3. The VCM of claim 1,wherein a moving section of the rotor is longer than an effective focussection of the lens, and the effective focus section is formed betweenthe moving sections of the rotor.
 4. The VCM of claim 3, wherein asection corresponding to each side of the effective focus section in themoving sections is an ineffective focus section.
 5. The VCM of claim 3,wherein the effective focus section is formed at a position discrete 5μm˜20 μm from an upper surface of the base.
 6. The VCM of claim 5,wherein the effective focus section is formed at a position discrete 10μm from an upper surface of the base.
 7. The VCM of claim 5, wherein theeffective focus section includes an infinite focus.
 8. The VCM of claim1, further comprising a cover coupled to the base to wrap the stator andthe rotor, and the effective focus section is formed at a positiondiscrete 5 μm˜20 μm from an inner lateral surface of the cover oppositeto the lens.
 9. The VCM of claim 8, wherein the effective focus sectionis formed at a position discrete 10 μm from an inner surface of thecover.
 10. The VCM of claim 8, wherein the effective focus sectionincludes a diopter (close-up) focus.
 11. The VCM of claim 10, wherein adriving signal at the close-up focus is 20 [mA].
 12. The VCM of claim 1,wherein an initial driving current for driving the rotor is 0 [mA]. 13.The VCM of claim 1, wherein a tilting amount of the rotor at theeffective focus section in response to a current amount provided to anyone of the first and second driving units is smaller than a tilingamount of the rotor at an ineffective focus section formed at an outsideof the effective focus section.
 14. The VCM of claim 13, wherein thetilting amount at the effective focus section is substantially zero. 15.The VCM of claim 1, wherein the elastic member includes a first elasticmember coupled to a bottom surface of the rotor and a second elasticmember coupled to an upper surface of the rotor opposite to the bottomsurface of the rotor.
 16. The VCM of claim 15, wherein each of the firstand second elastic members has a mutually different spring constant (K)in order to inhibit a tilt generated by a gravity center of the rotorwhile the rotor is driven.
 17. The VCM of claim 16, wherein the firstelastic member has a first spring constant in a case the gravity centerof the rotor is formed close to the second elastic member based on acenter of the rotor, and the second elastic member has a second springconstant greater than the first spring constant to inhibit the rotorfrom being tilted.
 18. The VCM of claim 17, wherein the second springconstant increases in proportion to a length between a center of therotor and the gravity center of the rotor, and the first spring constantdecreases in reverse proportion to the second spring constant.
 19. TheVCM of claim 17, wherein the first elastic member is formed with a firstcross-section, and the second elastic member is formed with a secondcross-section greater than the first cross-section.
 20. The VCM of claim17, wherein the first elastic member is formed with a first length at anelastic force-generating area, and the second elastic member is formedwith a second length longer than the first length at an elasticforce-generating area.
 21. The VCM of claim 17, wherein each of thefirst and second elastic members is formed with a mutually differentshape.
 22. The VCM of claim 16 wherein the second elastic member has afirst spring constant in a case the gravity center of the rotor isformed close to the first elastic member based on a center of the rotor,and the first elastic member has a second spring constant greater thanthe first spring constant to inhibit the rotor from being tilted. 23.The VCM of claim 22, wherein the second spring constant increases inproportion to a length between a center of the rotor and the gravitycenter of the rotor, and the first spring constant decreases in reverseproportion to the second spring constant.
 24. The VCM of claim 22,wherein the first elastic member is formed with a first cross-section,and the second elastic member is formed with a second cross-sectionsmaller than the first cross-section.
 25. The VCM of claim 22, whereinthe second elastic member is formed with a first length at an elasticforce-generating area, and the first elastic member is formed with asecond length shorter than the first length at an elasticforce-generating area.
 26. The VCM of claim 15, wherein the firstelastic member includes a first inner elastic unit coupled to the rotor,a first external elastic unit arranged outside of the first innerelastic unit, and a first connection elastic unit connecting the firstinner elastic unit and the first external elastic unit, and the secondelastic member includes a second inner elastic unit coupled to therotor, a second external elastic unit arranged outside of the secondinner elastic unit, and a second connection elastic unit connecting thesecond inner elastic unit and the second external elastic unit.
 27. TheVCM of claim 15, wherein each of the first and second elastic membershas a mutually different spring constant (K) in order to inhibit therotor from being tilted by offsetting a moment of the rotor generated bya gravity center of the rotor lop-sided to one side from the center ofthe rotor.
 28. The VCM of claim 2, wherein a length of a first stroke toa first direction of the rotor is differently formed from a length of asecond stroke to a second direction of the rotor.
 29. The VCM of claim28, wherein the length of the first stroke is formed shorter than thelength of the second stroke.
 30. The VCM of claim 28, wherein the lengthof the first stroke is formed longer than the length of the secondstroke.
 31. The VCM of claim 28, wherein a ratio between the firststroke length and the second stroke length is at 1:2˜1:3.
 32. The VCM ofclaim 28, wherein an optical axis of the lens is arranged in parallelwith a ground surface, and the base is arranged perpendicular to theground surface.
 33. The VCM of claim 28, wherein an optical axis of thelens is arranged perpendicular to a ground surface, and the base isarranged opposite to the ground surface.
 34. The VCM of claim 28,wherein an optical axis of the lens is arranged perpendicular to aground surface, and the cover wrapping the stator and the rotor isarranged opposite to the ground surface.
 35. The VCM of claim 1, whereina first central part bisecting an upper surface of the rotor and thebottom surface of the rotor, and a second central part opposite to anupper surface of the base and the base, and bisecting a distance of aninner surface of the cover wrapping the stator and the rotor aredislocatedly formed.
 36. The VCM of claim 35, wherein the first centralpart is arranged at a bottom surface of the second central part.
 37. TheVCM of claim 35, wherein the first central part is arranged at an uppersurface of the second central part.
 38. The VCM of claim 35, wherein afirst gap between the base and the rotor is narrower than a second gapbetween the cover and the rotor.
 39. The VCM of claim 35, wherein thesecond gap is twice or thrice greater than the first gap.
 40. The VCM ofclaim 1, further comprising a shock absorption member arranged on thebase opposite to the rotor.
 41. The VCM of claim 40, wherein the shockabsorption member includes any one material selected from a group of asponge, a synthetic rubber having elasticity and a rubber.
 42. The VCMof claim 1, wherein the first driving unit includes a magnet, and thesecond driving unit includes a coil generating a magnetic field inresponse to a current.
 43. The VCM of claim 1, wherein the first drivingunit includes a coil generating a magnetic field in response to acurrent, and the second driving unit includes a magnet.